U.S. patent application number 11/801424 was filed with the patent office on 2008-08-07 for location of basestation.
This patent application is currently assigned to Ubiquisys Limited. Invention is credited to Andrea Giustina, Edward Hatala.
Application Number | 20080188243 11/801424 |
Document ID | / |
Family ID | 37891252 |
Filed Date | 2008-08-07 |
United States Patent
Application |
20080188243 |
Kind Code |
A1 |
Giustina; Andrea ; et
al. |
August 7, 2008 |
Location of basestation
Abstract
A basestation for a cellular communication system is intended
for purchase and deployment by a customer, rather than by the
network operator. After installation, the position of the
basestation is determined by detecting signals transmitted by
neighbouring basestations. By detecting a position relative to
multiple neighbouring basestations, the location of the basestation
can be determined to a sufficient degree of accuracy.
Inventors: |
Giustina; Andrea; (Milan,
IT) ; Hatala; Edward; (Devizes, GB) |
Correspondence
Address: |
BEYER WEAVER LLP
P.O. BOX 70250
OAKLAND
CA
94612-0250
US
|
Assignee: |
Ubiquisys Limited
|
Family ID: |
37891252 |
Appl. No.: |
11/801424 |
Filed: |
May 8, 2007 |
Current U.S.
Class: |
455/456.6 |
Current CPC
Class: |
G01S 5/0242 20130101;
H04W 60/00 20130101; H04W 36/0061 20130101; H04W 64/003 20130101;
H04W 84/045 20130101; H04W 48/04 20130101; H04W 24/02 20130101;
H04W 64/00 20130101; H04W 88/08 20130101 |
Class at
Publication: |
455/456.6 |
International
Class: |
H04Q 7/20 20060101
H04Q007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 2, 2007 |
GB |
0702095.1 |
Claims
1. A method of determining a location of a basestation in a
communications network, the method comprising: detecting signals
transmitted by a plurality of neighbouring basestations;
determining a location of said basestation relative to each of said
plurality of neighbouring basestations; and determining the
location of the basestation based on said determined relative
locations.
2. A method as claimed in claim 1, comprising determining the
location of said basestation relative to each of said plurality of
neighbouring basestations based on the strengths of signals from
said neighbouring basestations.
3. A method as claimed in claim 1, comprising determining the
location of said basestation relative to each of said plurality of
neighbouring basestations based on the timings of signals from said
neighbouring basestations.
4. A method of preventing use of a SIM card in more than one
basestation of a communications network, the method comprising:
associating a unique identifier of said SIM card with a unique
identifier of a basestation; and allowing operation of said
basestation only when an allowed association exists between the SIM
card and said basestation.
5. A method of determining a position of a mobile
telecommunications device, the method comprising: when the mobile
communications device has a connection to a femtocell basestation
in a mobile communications network, determining a location of the
femtocell basestation; and taking the location of the femtocell
basestation as the position of a mobile telecommunications
device.
6. A method as claimed in claim 5, wherein the step of determining
the location of the femtocell basestation comprises: determining
the location of the femtocell basestation based on signals received
from other basestations in said mobile communications network.
7. A method as claimed in claim 5, wherein the femtocell
basestation has a connection to a packet data network at a known IP
address, and the step of determining the location of the femtocell
basestation comprises: determining a physical address associated
with the known IP address; and determining the location of the
femtocell basestation based on said physical address.
8. A method of determining whether a basestation in a
communications network has changed position, the method comprising:
at a first time, detecting signals transmitted by a plurality of
neighbouring basestations; at a second time, detecting signals
transmitted by a plurality of neighbouring basestations;
determining whether the basestation has changed position based on
the detecting signals at the first time and at the second time.
9. A method as claimed in claim 8, wherein: the step of detecting
signals transmitted by the plurality of neighbouring basestations
at the first time comprises identifying said neighbouring
basestations at the first time; the step of detecting signals
transmitted by the plurality of neighbouring basestations at the
second time comprises identifying said neighbouring basestations at
the second time; and the step of determining whether the
basestation has changed position comprises determining whether the
neighbouring basestations identified at the first time are
substantially the same as the neighbouring basestations identified
at the second time.
10. A method as claimed in claim 9, wherein said plurality of
neighbouring basestations comprise basestations in a plurality of
mobile networks.
11. A method of determining a location of a basestation in a
communications network, the method comprising: requesting that a
mobile device connected to the basestation detect signals
transmitted by a plurality of neighbouring basestations; and
determining the location of the basestation based on reported
measurements of said signals.
12. A method as claimed in claim 11, comprising obtaining GSM
measurements from at least one mobile device connected to the
basestation.
13. A method of determining a location of a basestation in a
communications network, the method comprising: requesting that a
mobile device connected to the basestation report its own location,
as determined by a positioning system; and determining the location
of the basestation based on the reported location.
Description
[0001] This invention relates to a basestation for a cellular
communication system, and in particular to a method and a system
for determining the location of the basestation.
[0002] There are situations in which it may be essential or highly
desirable to know the position of a basestation in a cellular
communication system. For example, when an emergency call is made
through the basestation, it may be a requirement that the emergency
services be informed of the location of the basestation, in order
that they can attend the emergency. In addition, knowing the
location of the basestation, and hence knowing at least
approximately the location of a mobile device that has a connection
to that basestation, allows the mobile network operator to offer
location-based services to the mobile device user.
[0003] In existing cellular communication systems, basestations are
constructed and commissioned by the mobile network operators
themselves, and so the mobile network operators always know exactly
where the basestations are located.
[0004] Femtocell basestations are now proposed, which can be
purchased by consumers for use within their own homes or offices,
using their own existing broadband internet connection to provide
backhaul into the core network of the mobile network operator. In
such situations, the mobile network operator may not know where
exactly the femtocell basestation has been positioned.
[0005] According to the present invention, there are provided
methods for use in a basestation of a mobile communications
network, or in the network itself, for determining information
about the position of the basestation itself, and for determining
the position of mobile devices having a connection to the
basestation. Where the basestation has a small coverage area,
information about the position of the basestation can be taken as
an acceptably accurate estimate of the position of the mobile
device and, conversely, information about the position of the
mobile device can be taken as an acceptably accurate estimate of
the position of the basestation.
[0006] According to other aspects of the invention, there are
provided basestations and network nodes for performing these
methods.
[0007] FIG. 1 is a block schematic diagram, illustrating a part of
a cellular wireless communications network in accordance with an
aspect of the present invention.
[0008] FIG. 2 is a block schematic diagram of a basestation in
accordance with an aspect of the present invention.
[0009] FIG. 3 is a flow chart, illustrating a first method in
accordance with the present invention.
[0010] FIG. 4 is a flow chart, illustrating a second method in
accordance with the present invention.
[0011] FIG. 5 is a flow chart, illustrating a third method in
accordance with the present invention.
[0012] FIG. 1 illustrates a part of a cellular wireless
communications network in accordance with an aspect of the present
invention. Specifically, FIG. 1 shows a core network (CN) 10 and a
radio network (RN) 12 of a cellular wireless communications
network. These are generally conventional, and are illustrated and
described herein only to the limited extent necessary for an
understanding of the present invention.
[0013] Thus, the core network 10 has connections into the Public
Switched Telephone Network (PSTN) (not shown) and into a packet
data network, for example the internet 14. The radio network 12 may
include, for example, a GSM radio network and/or a UMTS radio
network, which are then generally conventional. As shown in FIG. 1,
the radio network 12 has a number of basestations (BS) 16a, 16b,
16c connected thereto.
[0014] As will be recognized by the person skilled in the art, a
typical radio network 12 will have many such basestations connected
thereto. These basestations provide coverage over respective
geographic areas, or cells, such that a service is available to
subscribers. Often, there is a group of basestations that together
provide coverage to the whole of the intended service area, while
other basestations provide additional coverage to smaller areas
within that intended service area, in particular to smaller areas
where there is expected to be more demand for the service. The
cells served by the basestations of the first group are then
referred to as macrocells, while the smaller areas served by the
additional basestations are referred to as microcells.
[0015] FIG. 1 also shows an additional basestation 18 that can be
used to provide coverage over a very small area, for example within
a single home or office building. This is referred to as a
femtocell basestation (FBS). The femtocell basestation 18 is
available for purchase by a customer from a general retail outlet
and, after purchase, can be connected into the mobile network
operator's core network 10 over the internet 14, by means of the
customer's existing broadband internet connection 20. Thus, a user
of a conventional mobile phone 22 can establish a connection
through the femtocell basestation 18 with another device, in the
same way that any other mobile phone can establish a connection
through one of the other basestations of the mobile network
operator's network, such as the basestations 16a, 16b, 16c.
[0016] As shown in FIG. 1, the core network 10 includes a
management system (MS) 11, which is provided specifically for
managing the femtocell basestation 18 and the other femtocell
basestations that are active in the network.
[0017] As mentioned above, the macrocell basestations provide
coverage to the whole of the intended service area including the
location of the femtocell basestation 18 and the location of the
mobile phone 22 while it is in the coverage area of the femtocell
basestation 18.
[0018] This property is used in aspects of the present invention,
as will be described in more detail below.
[0019] In one embodiment of the invention, the customer's broadband
internet connection 20 is provided by an internet service provider
(ISP) 60 over infrastructure provided by a wholesale service
provider (WSP) 62 using DSL (Digital Subscriber Line) technology,
the same infrastructure being used to make landline telephone
calls. Each broadband line, such as the line 20, is identified by a
Manufacturers Authentication Code (MAC), while the internet service
provider (ISP) knows the customer's IP address. At the same time,
the line is identified by a Calling Line Identity (CLI), which is
used to indicate the customer's landline telephone number. There is
a mapping between the Manufacturers Authentication Code (MAC) and
the Calling Line Identity (CLI), and at least one of the internet
service provider (ISP) and the wholesale service provider (WSP) is
able to associate at least one of the Manufacturers Authentication
Code (MAC) and the Calling Line Identity (CLI) with the customer's
physical address.
[0020] In one embodiment of the invention, therefore, the physical
location of the femtocell basestation 18 can be determined from the
IP address that it is using.
[0021] In this and other embodiments of the invention, the physical
location of the femtocell basestation can be determined
periodically, and an alert can be provided when this physical
location is determined to have changed. This alert can for example
be used to prevent further usage of the femtocell basestation, or
to restrict the available services.
[0022] Further, since the femtocell basestation is intended to
operate with low power, and hence with a short range (for example
in the range 10 m-25 m), the physical location of the femtocell
basestation that has been determined gives an estimate of the
location of any mobile device that has a connection to the
femtocell basestation, and this estimate is sufficiently accurate
for most purposes.
[0023] More specifically, in one embodiment of the invention, the
radio network 12 includes an SMLC (Serving Mobile Location Center)
64, that is able to calculate the location of the femtocell
basestation or the connected mobile device, as described in more
detail below. Further, the core network 10 includes a GMLC (Gateway
Mobile Location Center) 66 that is able to store and retrieve
location information.
[0024] FIG. 2 is a schematic diagram, illustrating in more detail
the form of the basestation 18. The basestation has an antenna 23,
connected to a duplexer 24. In the case where the cellular wireless
network operates on the frequency division duplex principle, where
each device can simultaneously transmit and receive radio frequency
signals on a pair of frequencies having a known relationship, the
duplexer is effectively a pair of matched filters that allow
signals at the system downlink frequencies (that is, the transmit
frequencies of the basestation 18) to be passed to the antenna 23,
and allow signals at the system uplink frequencies (that is, the
receive frequencies of the basestation 18) to be passed from the
antenna 23.
[0025] In addition, in preferred embodiments of the present
invention, the basestation 18 is also able to detect signals
transmitted by other basestations, such as the basestations 16a,
16b, 16c, at allocated system downlink frequencies. For example,
the basestation 18 may be provided with separate receiver
circuitry, corresponding to the receiver circuitry conventionally
found in a user device such as a mobile phone, or further means may
be provided for allowing signals at the system downlink
frequencies, received at the antenna 23, to be received in the
basestation 18.
[0026] The basestation 18 includes a signal processor 26. In the
case of signals for transmission by the basestation 18, the signal
processor 26 receives the digital signals, converts them to the
required format based on the communications standard used by the
basestation, and passes the signals to transmit RF circuitry (TX)
28. As is generally conventional, the transmit RF circuitry 28
converts the signals to analog form, and upconverts them to the
required radio frequency using an oscillator signal supplied by
synthesizer circuitry 30 at a downlink frequency F.sub.dl. The RF
signals can then be passed through the duplexer 24 to the antenna
23 for transmission.
[0027] In the case of signals transmitted by a mobile device having
a connection with the basestation 18, the signals are received at
the antenna 23, and passed through the duplexer 24 to receive RF
circuitry (RX) 34. As is generally conventional, the receive RF
circuitry 34 downconverts the signals from the relevant radio
frequency using an oscillator signal supplied by the synthesizer
circuitry 30 at an uplink frequency F.sub.ul, and converts them to
digital form. The digital signals are then passed to the signal
processor 26.
[0028] In accordance with the present invention, the basestation 18
uses information derived from signals transmitted by other network
nodes, in particular the macrocell basestations 16a, 16b, 16c
and/or any attached mobile phone 22 within the coverage area of the
femtocell basestation 18, in order to optimize its own
operation.
[0029] The basestation 18 operates under the control of a
controller 50, to which is connected an interface 52 for a SIM
card, or other module containing subscriber data. A suitable SIM
card will typically be supplied to the customer on purchase of the
basestation 18, and this SIM card can be used to identify the
basestation 18 uniquely. As it can contain a SIM card, the
basestation 18 can itself perform some of the functions of a user
equipment, and can be recognized as a user equipment by the
network.
[0030] There are various reasons why it may be necessary for the
network to know the location of the basestation 18, and more
specifically the location of the SIM card. For example, when an
emergency call is made by a mobile phone connected to the
basestation 18, the mobile network operator should preferably be
able to indicate the location of the calling device. Where, as
here, the femtocell basestation 18 has only a short range (for
example, the range may be approximately 25 m, or the femtocell
basestation may provide coverage only within one particular
building), it may be sufficient to provide the emergency services
authorities with the location of the femtocell basestation.
[0031] Also, while the femtocell basestation 18 may be supplied to
the customer by the mobile network operator together with a SIM
card, and while it may be advantageous for that SIM card to be
removable from the basestation 18, in the same way that SIM cards
are typically removable from mobile phones, it may nevertheless be
highly undesirable for the mobile network operator that the SIM
card should be able to be inserted in a different basestation.
Similarly, it may be highly undesirable for the mobile network
operator that the basestation 18 should be operated from a
non-approved location, for example outside the country where the
mobile network operator has an operating license.
[0032] FIG. 3 is a flow chart, illustrating a first method for
determining the location of the basestation 18. In step 30, when
the basestation 18 is purchased by the customer, either in a retail
outlet or remotely (for example, over the internet), an address is
recorded. In step 32, this recorded address is stored in a database
within the management system, and associated with data that
uniquely identifies the basestation 18, such as the unique Network
Interface Controller (NIC) number associated with the basestation
18, or the unique International Mobile Subscriber Identifier (IMSI)
associated with the SIM card in the basestation 18 (if it can be
assumed that the SIM card cannot be, or has not been, removed from
the basestation 18).
[0033] In step 34 of the process, this stored address is activated
when the basestation 18 first connects to the network, informing
the mobile network operator that it is operational.
[0034] In some cases, it will be acceptable for the mobile network
operator to use this stored address as the address at which the
basestation 18 is in operation.
[0035] In order to provide a higher degree of confidence that the
location of the basestation 18 is correct, additional steps can be
taken, and FIG. 4 is a flow chart illustrating such a process. It
will be apparent that certain steps of this process must be
performed in the basestation 18, while other steps of the process
must be performed in the management system 11 or another network
node, while still further steps may be performed either in the
basestation 18, or in the management system 11, or in another
network node, as seems appropriate.
[0036] In step 40, the basestation 18 measures specified parameters
in the signals transmitted from neighbouring basestations (for
example the basestations 16a, 16b, 16c in the network illustrated
in FIG. 1). For example, the measured parameters may relate to the
strengths of specified signals transmitted by such neighbouring
basestations.
[0037] The parameters to be measured may also include the cell-ID
of each of the macrocells seen. This may only allow the location of
the basestation 18 to be determined to a precision of a few
kilometres, but this may be enough in some situations.
[0038] The basestation 18 may also detect the SFN-SFN observed time
difference between detected signals. This can then be used
according to the OTDOA (Observed Time Difference on Arrival) method
to derive the location of the basestation 18.
[0039] Thus, the basestation 18 is able to identify the
neighbouring basestations, and to obtain some information from the
signals transmitted from those basestations. As mentioned above,
the basestation 18 is preferably able to detect signals transmitted
by other basestations, such as the basestations 16a, 16b, 16c, at
allocated system downlink frequencies, either by interrupting its
own transmissions, or by including separate receiver circuitry that
is operational in parallel with the receiver circuitry used for
handling calls.
[0040] In step 41, specified radio parameters are obtained from the
macrocell basestations identified by the basestation 18 in step 40.
For example, where the parameters measured in step 40 relate to the
strengths of specified signals transmitted by the neighbouring
basestations, the parameters obtained in step 41 may relate to the
known powers with which such signals are transmitted by the
neighbouring basestations. The basestation 18 may be able to obtain
the radio parameters of neighbouring basestations operated by
different operators and using different technologies such as GSM,
UMTS, etc. In one example, these measured parameters are
transmitted from the basestation 18 to the management system 11 for
it to use in determining the location of the basestation 18.
[0041] Further, the locations of these macrocell basestations will
be known to the mobile network operator, and will be stored in an
appropriate form (for example in the form of geographic X-Y
coordinates) in a database. In step 42, location information is
therefore retrieved from the database for the macrocell
basestations identified by the basestation 18 in step 40.
[0042] Based on this information, in step 43, the location of the
basestation 18 can be calculated, or at least can be estimated to a
sufficiently high degree of accuracy. For example, where the
measured parameters of the signals relate to signal strengths, or
relate to transit times of the signals, it is possible to calculate
or estimate the distance of the basestation 18 from each of the
neighbouring basestations from which such signals are detected.
Then, provided there are at least three such neighbouring
basestations, it is possible to use the well known technique of
triangulation to calculate or estimate the location of the
basestation 18 in the same geographic X-Y coordinates.
[0043] In step 44, the previously recorded operating address of the
basestation 18, which may for example have been stored in the form
of a street address or postal code, is converted to geographic
coordinates in the same coordinate scheme.
[0044] In step 45, the geographic coordinates of the basestation,
as derived in step 43, are compared with the geographic coordinates
of the user address obtained in step 44. Appropriate action is then
taken. If the derived geographic coordinates match the geographic
coordinates corresponding to the recorded address, to within an
acceptable tolerance, then it is assumed that the recorded address
is correct. For many purposes, it is then convenient to record the
location of the basestation 18 in the geographic coordinates.
[0045] If the derived geographic coordinates do not match the
geographic coordinates corresponding to the recorded address, to
within an acceptable tolerance, this implies that the basestation
18 is being used in a non-approved location. In such circumstances,
an alarm signal may be sent to the mobile network operator, and it
may be appropriate to discontinue service to the basestation 18
until its position changes again.
[0046] This process can be performed at regular intervals while the
basestation 18 is active.
[0047] A determination as to whether the basestation 18 has changed
its position can then be made by comparing some of the measured
parameters, without needing to determine the position exactly on
either occasion. For example, detecting the cell-ID of each of the
detected neighbour macrocells at different times should still give
the same list of neighbour macrocells, and a significant change may
be due to a change in the position of the basestation 18. In such a
situation, a significant change could perhaps also be due to a
change in the network planning of the mobile network operator, and
so the reliability of this technique is improved by detecting the
cell-ID of each nearby macrocells in a plurality of mobile
networks.
[0048] As mentioned above, another issue is that a SIM card could
be removed from a basestation, such as the basestation 18 at one
location, and then inserted in a different basestation at another
location, potentially enabling the user to obtain the same
services, to the possible disadvantage of the mobile network
operator.
[0049] FIG. 5 is a flow chart, illustrating a mechanism for
inhibiting the use of a SIM card in another basestation in such
circumstances. The mechanism makes use of the unique Network
Interface Controller (NIC) number associated with the basestation
18, and the unique International Mobile Subscriber Identifier
(IMSI) associated with the SIM card in the basestation 18.
[0050] In step 50, the basestation 18 reads the IMSI number of the
SIM and the NIC number. In step 51, it then associates these two
numbers and sends them onto the management system 11.
[0051] In step 52, the management system 11 determines whether this
association is allowable. For example, if an attempt is made to
transfer the SIM from another basestation 18, for example at
another location, this results in the new basestation informing the
management system 11 of an association between its NIC number and
the SIM IMSI. The management system 11 therefore checks to
determine if the SIM IMSI is already associated with another NIC
number. If the SIM IMSI is in fact already associated with another
basestation, the management system 11 inhibits the use of this new
basestation. For example, the management system 11 may send a
message to the new basestation to send a SMS message to the user
informing them that the basestation is locked and that they should
contact the mobile network operator, which they could possibly be
permitted to do through the basestation.
[0052] However, assuming that the association is allowable, in step
53 the management system 11 returns a message the basestation 18
that tells the basestation 18 to allow this particular SIM IMSI
number to work only with the basestation having that particular NIC
number, thereby locking them together.
[0053] For maintenance purposes there could be provided a
maintenance SIM, which might need to be used in many basestations,
and which would therefore be recognizable by each basestation, such
that the basestation does not go through this SIM/NIC validation
process when the maintenance SIM is inserted in the
basestation.
[0054] The process shown in FIG. 4 relies on the basestation 18
detecting signals from neighbour basestations. However, in other
situations, such measurements are not available, either because the
basestation is not able to detect signals on system downlink
frequencies, or because the macrocell coverage in the indoor
environment of the basestation is inadequate. In that situation,
the basestation can advantageously request, and receive,
measurement reports from one or more mobile device connected to the
basestation 18.
[0055] Then, the basestation 18 can assume that triangulation based
on measurements from one or more of the mobile devices is
reasonably accurate, for example because the mobile devices may be
able to detect signals from a larger number of macrocells. For
example, the mobile devices may be able to access GSM macrocell
measurements, even when the basestation 18 is not, either because
the GSM signal has better indoor coverage, or because the
basestation 18 is able to detect signals on the UMTS system
downlink frequencies but not on the GSM system downlink
frequencies.
[0056] In addition, one of the mobile devices may be provided with
A-GPS (Assisted Global Positioning System) technology, in which
case a highly precise position measurement may be available.
[0057] The basestation 18 can obtain a position detection signal
from one or mobile devices at a particular time, and can store this
location until it is confident that a better signal is
available.
[0058] There are therefore provided techniques for determining the
location of a basestation 18 and its attached mobile devices.
* * * * *